Amido-carboxylic acids are industrial chemical intermediates for the preparation of many chemicals used in commerce. For example, amido-carboxylic acids are used to make bleach activators for detergents. Amido-carboxylic acids are generally prepared by reacting a lactam or an amino acid with a carboxylic acid.
U.S. Pat. No. 2,453,234 discloses a process for preparing an amino-carboxylic acid by hydrolyzing a lactam by means of at least 10 moles of water per mole of lactam to produce an amino-carboxylic acid. Great Britain Pat. No. 648,889 discloses a process for preparing amino-carboxylic acids by heating aliphatic or cyclo-aliphatic lactams in the presence of more than 20 moles of water per mole of lactam. U.S. Pat. No. 2,956,068 discloses a process for preparing amido-carboxylic acids by reacting a lactam with a free carboxylic acid in the presence of catalytic amounts of water. The reaction product is obtained as a solid crystal mass which is subsequently suspended in water and neutralized.
Amido-carboxylic acids prepared by processes as mentioned above are purified either by crystallization or by solvent leaching. In solvent leaching, the solid amido-carboxylic acids are suspended in an organic solvent, filtered and washed. The slurry/wash procedure is repeated. The disadvantage of these purification processes are that low yields of the amido-carboxylic acid product is obtained.
In contrast, the present inventors have unexpectedly discovered a liquid/liquid extraction process for purifying amido-carboxylic acids which generates a high yield of the amido-carboxylic acid.